Protection of dispersed asbestos



l. J. NOVAK 2,675,745 PROTECTION OF DISPERSED ASBESTOS FIBERS ONPAPERMAKING MACHINES Filed Sept. 10, 1949 April 20, 1954 Patented Apr.20, 1954 PROTECTION OF DISPERSED ASBESTOS FIBERS ON'PAPERMAKINGMA'CHINES Izador J. Novak, Trumbully-Cozm' asslgnor toRaybestos-Manhattan, Ina, Passaic, N. L, a corporation of New J ersey-Application September 10, 1949, Serial No. 114,949

Claims.

This invention relates to improvements in the production of feltedsheets or webs of fibrous asbestos with generally conventionalpaper-making apparatus when employing slurries of individualized anddispersed asbestos produced in accordance with my co-pendingapplication, Ser. No. 66,552, filed December 21, 1948, now Patent No.2,626,213.

More particularly, the present invention relates to the maintenance andprotection of the asbestos fibers in such dispersed condition, asdistinguished from a flocked or clotted condition while on theforaminous or porous forming or conveying components of the paper-makingmachine, such as the Fourdrinier wire or felts thereof.

As more fully described in my aforesaid copending application, theasbestos dispersions with which the present invention is concerned areprepared by opening and individualizing the fibers of Chrysotileasbestos by subjecting macroscopic bundles or agglomerates thereof(which terms are intended to include mechanically fiberized asbestos) tomild mechanical action, such as stirring or agitation, while immersed inwater containing an organic detergent surface-active material adsorbableon the asbestos and capable of forming an alkaline dispersion therewith,the amount of detergent being in excess of that adsorbed on the asbestosand suflicient to form and preserve or maintain the dispersion in astable manner. Typical examples of such dispersing agents are Aerosol OT(dioctyl sodium sulfosuccinate), sodium oleate, and others more fullyparticularized in my said co-pending application. Treatment of theasbestos in this manner causes separation, individualization,dissemination and unclotting of the asbestos fibers, and converts themto single fibers or fascicular fiber bundles instead of thepredominantly clotted and tangled multiple fiber groups known to priorwet or dry asbestos practice. The fibers in such dispersion are in alubricated, slippery, relatively slidable condition and composedpredominantly of asbestos fibers of unit size, or fibro-colloidaldiameter, that is, of a diameter of from about 200 to about 500 Angstromunits.

As further set forth in my aforesaid co-pending application, for eachsurface-active agent, there concentrated agent. However, in addition tothe .minimum amount required and adsorbed by the asbestos, a furtherconcentration should remain in the liquid for the purpose of dispersinthe previously opened fibers, Thus, I have found that beyond the amountnecessary to satisfy the fibers, a certain concentration of the agent intheliqui'd phase is necessary to maintain a stable dispersion. Asfurther described and illustrated in my aforesaid c'o-pendingapplication, the concentration of the agent in the aqueous phasenecessary to maintain the asbestos dispersion over and be-' yondthatwhich is adsorbed by the asbestos is in the case of Aerosol OT about035% and for sodium oleate is .047%. These dispersions act in manyrespects like emulsions or dispersions of other substances in that eventhough a dispersion may contain an excess of dispersing agent in theliquid phase, dilution thereof by plain water in a rapid manner maycause precipitation or flocculation of the fibers. Further, the additionof water in an amount so as to reduce the concentration of theprotective agent or minimum amount required for dispersion will causeflocculation or precipitation of the fibers. As is evident from theforegoing, these surface-active agents are actually colloidizing agentsfor asbestos in an aqueous vehicle since they reduce the asbestos tocolloidal size particles and hold said particles in colloidaldispersion.

An object of the present invention to prevent the shocking of thedispersions employed, and to prevent flocking or precipitation of thefibers on the paper-making machine so as to permit felting of the fibersin their individualized dispersed condition whereby webs or sheets ofmuch greater toughness and flexibility can be produced, as compared todry webs or sheets composed of heretofore conventional or clottedasbestos fibers. It is a further object of the present invention toprevent clotting or precipitation of dispersed fibers in thepaper-making appurtenances such as Wires or felts so as to prevent theirbecoming clotted with asbestos fibers such as, for example, as mightoccur in carrying out the conventional water washing of a Fourdrinierwire on its return 'run.

For the purpose of illustration and not limitation, the following is anexample of a methodfor forming an asbestos dispersion, generallydescribed in my aforesaid co-pending application, and the sheetingthereof on a paper-making machine:

A slurry was prepared for making an asbestos tissue by adding 312 lbs.of 25% AerosolO'I' in water to .1000 gallons of water and dissolvingsame therein. Then 212 lbs. of 3B spinning grade Chrysotile asbestos wasadded and on stirring for four hours produced a smooth slurry at 2 /2%asbestos concentration. This was further diluted by adding water slowlyto the 2 /2 slurry in the volume proportion of 9 parts of 2 /2% slurryto 47 machine at 85 ft. per minute producing a tissue weighing about 0.7grams per square foot, having a thickness of about .00035 inch. Thistissue was well formed, smooth, uniform in fiber distribuand line 3| towhite water filter chest 32. This filter chest may, as illustrated, be acylinder or decker type of save-ah employing a wire-covered cylinder.The filtered white water is removed therefrom through line 33, valve 34and pump 35 and delivered through line 36 to the screen spray 31.

As an alternative, I may employ a fresh aqueous solution containing arequisite amount of asbestos dispersing agent, supplied from the tank 38by means of line 39 and valve 40 through pump 35 and line 36 to spray31. In such case, the asbestos dispersing agent need not necessarily be.the same one contained in the fiber dispersion,

tion, tough, strong, stretchy, and highly oriented in the machinedirection. On its return run the Fourdrinier wire was continuouslywashed with filtered white water recovered in the operation.

In this manner, the screen was continuously freed trates methods andmeans in connection there- W with for washing the Fourdrinier wire withwatercontaining dispersing agent in accordance with the presentinvention.

Referring to the drawing, a dilute slurry of dispersed andindividualized asbestos is supplied from the stock chest to the head boxI l wheref-rom it is picked up onto the Fourdrinier wire 12 by means ofthe suction formation roll [3. The Fourdrinier wire in conventionalmanner passes over the vacuum boxes Id and the felted asbestos .web onthe wire 12 is transferred therefrom as it passes over the drive roll I5bymeans of the pick- .up felt l6 as the latter passes over the suctionpick-up roll I]. The felt I6 is thereafter transferred from the web todrying means (not shown) such as, for example, a Yankee dryer.

The white water from the drainage trays l8 and i9 may be collectedthrough line and valve 2! to the white water tank 22 together with whitewater collected from the suction formation roll 13, vacuum boxes Hi andsuction pick-up roll I! by means of pump 23 and line 24. This whitewater may in whole or part be returned for use as make-up liquid throughthe pump 25, line 26, valve 21 and line 28 which may lead to suitablestock preparation tanks, or, in the alternative, if desired, discharged.

As i conventional, the Fourdrinier wire l2 in its lower return run as itpasses over rolls 29 is subjected to washing to clean the wire byremoving accumulations thereon. As previously "described and inaccordance with the present invention, washing of the Fourdrinier wireon its return run is accomplished by means of water containing asbestosdispersing agent. In accordance with the preferred embodiment of themes-.ent invention, such dispersing agent-containing water is the whitewater recovered as hereinbefore described. Thus, all or part of thewhltewater from line 26 may be directed through valvefiflbut still one, or amixture of asbestos dispersing agent, as described in my aforesaidco-pending application, capable of protecting the asbestos fibers fromclotting. If desired, the solution collecting in the pan l9 may bedischarged therefrom through line l2, valve 4| and line 42. As a furtheralternative, instead of discharging the solution from line 42 to waste,the discharge from line 42 may be recovered for use as slurry makeup or,as a further alternative, the discharge from line 42 may be directed bymeans, not shown, to tank 38 for direct recirculation thereof.

It will thus be seen that by proceeding in accordance with the preferredmethod, that is, by employing the white Water recovered in the usualmanner as the solution for washing the screen, an adequate amount ofdispersing agent in the wash water will already be present since suchamount was present in the slurry water for maintaining the dispersion,and in commercial practice the dispersing agent is generally containedtherein in exces so as to have insured stability of the originaldispersion.

As further indicated from the foregoing, if desired, wash water may beemployed which is not necessarily recovered white water. In suchinstance, the wash solution should contain an adequate amount ofdispersing agent, such as will not cause precipitation of fibers andentanglement thereof on the screen, th amount being related to thecharacter of the agent employed as hereinbefore pointed, out. In theevent the agent employed in this wash water solution is the same as theagent employed in preparing the original dispersion, it may be combinedwith the wash water. In the alternative, that is to say, for example, ifthe dispersing agent employed in the wash water is other than the agentemployed in preparin the original asbestor dispersion, it may be wastedafter use or recirculated in a separate but continuous wash system, ashereinbefore described in accordance with the description of theapparatus.

Although I have particularly described the present inmprovement inconnection with the washing of a Fourdrinier screen, it willbeunderstood that my invention is of like effect in respect to otherendless forming or conveying surfaces employed in paper-making machineswhich are intermittently or continuously washed. That is to say, washingoperations of surfaces on which my individualized and dispersedasbestor-fibers are deposited prior to drying should not'.. be

washed with clear water, or water deficientin an amount of dispersingagent adequate to maintain the fibers in their desired dispersedindividualized condition.

I claim as my invention:

'1. A method which comprises forming a fibrous asbestos web from anaqueous alkaline colloidal dispersion of individualized chrysotileasbestos fibers containing organic chrysotile asbestos colloidizingagent both adsorbed on the fibers and in the aqueous phase maintainingsaid dispersion, upon an endless continuously moving foraminatedsurface, continuously stripping the formed Web therefrom, and washingsaid surface, after removal of the web, with an aqueousdispersionmaintaining solution of asbestos colloidizing agent.

2. A method which comprises forming a fibrous asbestos web from anaqueous alkaline colloidal dispersion of individualized chrysotileasbestos fibers containing organic chrysotile asbestos colloidizingagent both adsorbed on the fibers and in the aqueous phase maintainingsaid dispersion, upon an endless continuously movin foraminated surface,continuously stripping the formed web therefrom, and Washing saidsurface after removal of the Web with a fresh aqueous solution of saidcolloidizing agent of a concentration substantially equal to that of theaqueous phase of said dispersion.

3. A method which comprises forming a fibrous asbestos web from anaqueous alkaline colloidal dispersion of individualized chrysotileasbestos fibers containin organic chrysotile asbestos colloidizin agentboth adsorbed on the fibers and in the aqueous phase maintaining saiddispersion, upon an endless continuously moving foraminated surface,continuously stripping the formed web therefrom, and Washin said surfaceafter removal of the Web, with white water containing said colloidizingagent recovered in the process.

4. A method which comprises forming a fibrous inated. surface,continuously stripping the formed web therefrom, collecting colloidizingagent-containing white Water separated in the process and filterin same,and Washing said foraminated surface, after removal of the webtherefrom, with said filtered white water.

5. In a method of making a fibrous asbestos web wherein an aqueousalkaline colloidal dispersion of individualized chrysotile asbestosfibers containin organic chrysotile asbestos colloidizin agent bothadsorbed on the fibers and in the aqueous phase maintaining saiddispersion, is deposited on an endless continuously moving foraminatedsurface and the excess aqueous solution removed therefrom through saidsurface to form a fibrous web thereon, the improvement which comprisescollecting and filtering a portion of said aqueous solution and Washingsaid foraminated surface therewith in the path of its return travel.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,302,313 Coppage Apr. 29, 1919 1,907,616 Tucker May 9, 19332,068,219 Badollet Jan. 19, 1937 2,182,274 Baker et a1. Dec. 5, 19392,217,005 Clapp Oct. 8, 1940 2,220,386 Badollet Nov. 5, 1940 FOREIGNPATENTS Number Country Date 481,705 Great Britain Mar. 16, 1938 OTHERREFERENCES Chemistry of Pulp and Paper Making by Sutermeister, 3rd Ed.(1941), pgs. 407-411, pub. by John Wiley and Sons, New York.

Morrison, Paper Industry and Paper World, May 1943, p. 192.

1. A METHOD WHICH COMPRISES FORMING A FIBROUS ASBESTOS WEB FROM ANAQUEOUS ALKALINE COLLOIDAL DISPERSION OF INDIVIDUALIZED CHRYSOTILEASBESTOS FIBERS CONTAINING ORGAINC CHRYSOTILE ASBESTOS COLLOIDIZINGAGENT BOTH ADSORBED ON THE FIBERS AND IN THE AQUEOUS PHASE MAINTAININGSAID DISPERSION, UPON AN ENDLESS CONTINUOUSLY MOVING FORAMINATEDSURFACE, CONTINUOUSLY STRIPPING THE FORMED WEB THEREFROM, AND WASHINGSAID SURFACE, AFTER REMOVAL OF THE WEB, WITH AN AQUEOUSDISPERSIONMAINTAINING SOLUTION OF ASBESTOS COLLOIDIZING AGENT.